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-   -   Brossphate opal 5% (http://talk.craftweb.com/showthread.php?t=11861)

Jordan Kube 02-01-2018 06:50 PM

Brossphate opal 5%
 
So I melted this 5% opal the other day:

In pounds
Sand 7.3125
Soda Ash  2.38875
Potassium Carbonate 0
Calcium Carbonate 0.4125
Strontium Carbonate 0.675
Zinc Oxide 0.225
Alumina Hydrate 0.3375
Lithium Carbonate 0.075
Antimony 0.03975
Potassium Nitrate 0.075
Sodium Tripolyphosp. 0.93

Total 12.471

Oxides %
SiO2 66.86
Na2O 16.4
K2O 0.327
LiO 0.278
CaO 2.13
MgO 0.006
SrO 4.35
ZnO 2.06
Al2O3 2.229
P2O5 4.95
Sb2O5 0.365

Charged a few scoops at 2300 every two hours. Held at 2300 for 10 hrs and then down to 2150. It came out pretty scuzzy on top like you guys talk about some phosphates coming out. It was also pretty streaky in coloration and cordy looking. It blew out ok and the stuff I made into bar struck out beautifully after being picked up again, as always. As a note, I ground the STPP in a bullet blender in an effort to avoid some chunkies I was getting in the 2.5% melts. It also came out 4 points high after my educated guess on adjustment. Based on that and my percentages I'm thinking at least adding some silica is in order.

Any thoughts on cleaning this one up?

Pete VanderLaan 02-02-2018 08:44 AM

I'd be inclined to simply replace that calcium with both zinc and strontium and the industrial sludge will stop. I had told you it has a tendency to be streaky and more phosphate would help there. While the silica is low, it's not that low. I assume you're allowing the stuff to get really cold before you try for the strike.

I don't particularly trust flame annealed Hagy seals.

Jordan Kube 02-02-2018 11:21 AM

Thanks Pete, I'll give that a try.

As far as flame annealing Hagy seals, it's only so they don't crack before I get them into the annealer. They just don't look right and don't give good information if they are not properly annealed.

Pete VanderLaan 02-02-2018 01:16 PM

Mine don't crack before they go in the box but I'm not six points off.

There are people who rely on flame annealing, an all around bad idea.

As to the phosphate. I'm not sure what that will do. It seems to me that you should be able to make the phase separation work using that alumina which is key in fluorine opals as well. I don't know if you remember when I described the streaks to you last year and you were curious. It's quite compatible and I've had that cup around for years now. The fact that it strikes on a reanneal confirms that there's plenty in there.

Bob Held first noted that up to 5% bone ash would stay compatible with your clear way back at the NCECA conference in 1968- pre GAS. But it had to melt at over 2400F. It was a true calcium monophosphate which is really hard to find now. 2300 seems a bit cold to me on that stuff you're doing. Give it another 25 degrees.

Jordan Kube 02-02-2018 02:47 PM

Hotter was my other thought. Stuck in a wire melter for now. I ditched the borax Dave was using too.

Pete VanderLaan 02-02-2018 04:11 PM

If you're ditching the borax then you need to use another method of keeping that melt easy. Heat helps but if the borax goes, then add more heat. Sodium nitrate would be where I would look for chemical help. . Lithium could be increased but it's pricey.
My original phosphate melts needed 2450F and very small charges. That was 1975.

Dave Bross 02-05-2018 10:37 AM

I'm with Pete on the nitrate or lithium to replace the borax.

When I was experimenting with those I did a few melts with a lot of potassium nitrate (0.6 % up to 1%) and it upped the melt speed almost beyond belief.

I don't know what a nice compromise would be between fast clean melt at high percentages and wear and tear on the pot. I did a number of melts with the 0.6% and a few gradually upping the percentage with no sign of any worse pot damage than usual. That was using assay pots, which dissolve quickly if anything is too rough on them. I always liked that about assay pots. Canary in the coal mine if you will. I remember one batch of Phillips high COE Moretti matching batch that ate the assay pot down to paper thin in three melts.

You're using a lot of phosphorous there too. Are you gaining more in density than you might get with an extra strike/s on the lower percentage formula or are you after a one strike wonder?

Pete VanderLaan 02-05-2018 03:27 PM

Once you're getting into this type of melt, assay pots in a high use situation is probably not the best solution.

Jordan Kube 02-05-2018 06:08 PM

Thanks for the help guys, I'll give those things a try. I'm using a CC pot and it's holding up pretty well. Those 38 pound pots are just the perfect small pot.

Dave, yes, trying for more density, one strike wonder. When I make it into bar and pick it back up it is perfectly wonderful and homogeneous. The stuff out of the pot is gorgeous too, just a different animal. What if I melted a pot, scooped it out and then remelted it? Would the glass in the pot strike out like the bar? If no one has done this there is only one way to find out!!!

Pete VanderLaan 02-05-2018 06:12 PM

seeking out new worlds, going where no man has gone before...

Well not actually. Lino used to frequently suggest this.

Dave Bross 02-09-2018 03:36 PM

Yes, every time it cools and reheats it gets denser.

Kenny Pieper 02-09-2018 04:04 PM

I never use the phosphate as just an opciifier. I think the beauty of this color is when it is still translucent. That when you get the opal effect. I like it quite weak.

Pete VanderLaan 02-09-2018 05:01 PM

That's the light before dawn...

Marc Carmen 02-12-2018 10:09 PM

I'm with Kenny on light translucent route. In my experience, a nice thick layer of barely striking opaline as an underlay has a much more beautiful effect than relying on blowing a commercial color thin until translucent. Perhaps this approach allows more light scattering within the color layer. Just think of how beautiful a nice chunk of cast opaline glass looks. Also, a thick layer of lighter opaline in blown work is much less temperamental in terms of striking inconsistencies and tool marks, etc. To me that is the beauty of making your own opaline, the fact that you can use a very low amount of phosphate in your formula and then be generous with the amount of rod you use in each piece.

Jordan do you have pics of work made from this formula struck right from the pot? I always made my melts into color bar but it still seemed to strike dense if I took a gather over a cold crack-off moile at about 1.25% phosphate. Never really had to resort to boron or lithium. Replacing the rest of the calcium with barium may be all the fluxing action you need. I was using a wire melter too but never tried those higher %'s of phosphate.

Thanks Dave for that thread a few years back!

Eben Horton 02-13-2018 05:58 AM

The most beautiful phosphate opals I have seen are ones that look like a cross between Vaseline and mayonnaise. (How’s that for a visual? )
Whites with hints of slightly yellow and reddish hues within.

Pete VanderLaan 02-13-2018 06:44 AM

It should not strike right from the pot. That would indicate the presence of fluorine. Since a phosphate is a phase separation glass it takes a cooling cycle followed by a heating cycle to cause that occurrence. The curiosity of the stuff Jordan made and I had noted to him privately was that it was streaky, something I didn't like. It looked like someones combed hair.

Marc Carmen 02-13-2018 07:00 AM

Ohh the streaky part sounds interesting. Do you think the streaks just came from a layer of crud on the surface of the melt?

IMO fluorine totally screws up a phosphate opal but the color makers all seem to be doing it.

Kenny Pieper 02-13-2018 07:32 AM

I make goblets out of a phosphate opal and usually use the color right out of the pot. Well one day I got an order for a few of the opal goblets that I didn't have in stock so I made them out of a bar I had from the last melt. When they came out of the oven and I set them next to the other goblets I could see the ones made out of bar were not nearly as bright and lively. They were more gray. So now I only use that glass out of the pot. All about the thermal history!

Jordan Kube 02-13-2018 06:04 PM

Care to pass that one along Kenny? I'd be interested to see how the different chemicals affect that strike. Or if not, maybe compare against Dave's formula for us? I make goblets out of this stuff and barely get anything to happen.

Pete VanderLaan 02-13-2018 06:17 PM

look at two things. First Sodium tri poly phosphate. break that down.
Then look at trisodium phosphate, Break that down
The look at calcium mono phosphate. Break that down.

Then look at calcium phosphate as a phase separation issue. then look at apatite crystals and why they do what they do. Then count the stones. Then get it really hot and small charges. If you can get rid of the calcium and replace with strontium your day will go better. You can't get rid of all of it.

Jordan Kube 02-13-2018 07:44 PM

Would the strontium be a 1 to 1 substitution for calcium?

Greg Vriethoff 02-13-2018 09:11 PM

God, the stuff that I love.

Thank you!

Pete VanderLaan 02-14-2018 07:59 AM

Quote:

Originally Posted by Jordan Kube (Post 138521)
Would the strontium be a 1 to 1 substitution for calcium?

****
It should be fine if you notice that the expansion factors are so similar.

Jordan Kube 02-14-2018 03:32 PM

Alright, looks like I've got some work to do. I'm getting closer to a nice copper blue with silver. The third melt is happening today. The erbium glass is now almost dead on in expansion and hopefully will go into production. Second test for that next Tuesday. I'd really like to loosen it up a bit, it's pretty viscous stuff. I'm wondering if our good friend strontium could help?

Pete VanderLaan 02-14-2018 05:17 PM

My offhand thought is cryolite= sodium alumina hexafluoride/ Very small additives would reduce the melt conditions. It would slop it up. Otherwise sodium nitrate for the runny goblet people. . Either will push the expansion around.
What you need to be seeing is the phase separation reduction of Apatite crystals occurring because the calcium is being dropped. Trying to do this in essentially a production shop is really ambitious.

This is a phrase that really gets spell check maxed out. Now it wants appetite.


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